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    <h1>SCSI Media Changer and Backup Device Control System</h1>
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<p>
[Also see the SourceForge <a href="http://sourceforge.net/projects/mtx">
project page</a>.]
<p>
<i>mtx</i> is a set of low level driver programs to control features
of SCSI backup related devices such as autoloaders, tape changers,
media jukeboxes, and tape drives. It can also report much data,
including serial numbers, maximum block sizes, and TapeAlert(tm)
messages that most modern tape drives implement (to tell you the exact
reason why a backup or restore failed), as well as do raw SCSI READ
and WRITE commands to tape drives (not important on Linux, but
important on Solaris due to the fact that the Solaris tape driver
supports none of the additional features of tape drives invented after
1988). <i>mtx</i> is designed to be a low level driver in a larger
scripted backup solution, such as <a
href="http://amanda.sourceforge.net">Amanda</a>.
<i>mtx</i> is not
supposed to itself be a high level interface to the SCSI devices that
it controls.
<p> 
This version has the following features:

  <ul>
  <li> Will deal with LARGE media libraries (over a hundred elements).
  <li> Supports multi-drive media changers such as the Exabyte 220 dual-
drive tape library.
  <li> Supports the 'invert' bit for optical jukeboxes that need that in
order to flip their media.
  <li> Supports the 'eepos' bits for libraries that need this to extend/retract
their import/export tray. 
  <li> Now supports import/export elements!
   <li> Reports volume tags (bar codes) and "alternate volume tags"
(whatever those are!) for those tape libraries
that support them. 
<li> Now runs under FreeBSD and at least Solaris 8. 

<li> Now has a 'man' page!
<li> The actual SCSI manipulation has been separated out into a library, so
that you can create your own "C" programs that manipulate SCSI media changers
directly. (Please note: this is under GPL, so any such programs will have
to be under GPL also). 
</ul>

<p>
 This program supposedly supports FreeBSD, Solaris, Linux, HP/UX, and
IRIX. Tru64 Unix and VMS are probably irretrievably broken at this
time. This program has been tested under FreeBSD, Solaris, and Linux,
and there only with a limited set of hardware. See the COMPATIBILITY 
list in the source code.
</ul>
<h2> Source Code </h2>
The current source code is:
<ul>
<li> <a href="http://mtx.sourceforge.net/mtx-1.2.13.tar.gz">http://mtx.sourceforge.net/mtx-1.2.13.tar.gz</a>
</ul>
RPMs may be available from the following place:
<ul>
<li> <a href="http://rpmfind.net/linux/RPM/mtx.html">RPMfind's 'mtx' page</a>
</ul>
A .spec file is now included in the 'mtx' distribution for building your
own RPM's.
<p>
Note that RPMs
are courtesy of <a href="http://www.sewingwitch.com/ken/">Kenneth Porter</a>,
who should be contacted regarding rpm-related problems.
<p>

<h2> Known Bugs And Limitations </h2>
<ul>
<li> 
       You  may  need  to  do a 'mt offline' (or equivalent for your OS)
       on the tape drive to
       eject the tape before you can issue the 'mtx unload'  command.
The Exabyte EZ-17 and 220 in particular will happily
       sit there snapping the robot arm's claws around  thin  air
       trying to grab a tape that's not there.
<li> 
The 'next' command does not understand the 'invert' bit (i.e., does not
recognize that for optical jukeboxes, the 'next' of side one is to unload,
invert, and reload the same disk). It always advances to the next
slot instead. 
 <li>
       For  some  Linux distributions, you may need to re-compile
       the kernel to scan SCSI LUN's in order to detect the media
       changer. Check /proc/scsi/scsi to see what's going on.

<li> 
       If you try to unload a tape to its 'source' slot, and said
       slot is full, it will instead put the tape into the  first
       empty  slot.  Unfortunately the list of empty slots is not
       updated between commands on the command line,  so  if  you
       try to unload another drive to a full 'source' slot during
       the same invocation of 'mtx', it will try to unload to the
       same  (no  longer  empty)  slot  and  will urp with a SCSI
       error.

<li> For big tape libraries (more than a couple dozen elements) this
may set a big Allocation_Size in the SCSI command block for the
REQUEST_ELEMENT_STATUS command. Some operating systems may not be able
to handle this. Versions of Linux earlier than 2.2.6, in particular,
may fail this request due to inability to find contiguous pages of
memory for the SCSI transfer (later versions of Linux 'sg' device do
scatter-gather so that this should no longer be a problem).

<li> VMS and Tru64 support are probably irretrievably busted. 


<li> This program  will only use the first arm of multiple-arm robots unless
the robot re-maps all arms to one element ID. 

<li> It has been reported that this program works on Solaris 7 using the 'sst'
driver, and may work on Solaris 8 using the 'sgen' driver. 'sst' can
be gotten from the Amanda contrib directory at 
<a href="http://download.sourceforge.net/amanda/">http://download.sourceforge.net/amanda</a>.

</ul>

<h2> Philosophy </h2>
The Unix philosophy is "many small tools chained together". <i>mtx</i> supplies
those small tools so that you can create your own backup and 
recovery tools by chaining
<i>mtx</i> pieces together, whether it be with /bin/sh, Perl, Python, or
CAML.


<h2> Support </h2>
<ul>
<li>There is now a 'mtx' mailing list at <a href="http://sourceforge.net/projects/mtx/">http://sourceforge.net/projects/mtx/</a>. 
<li>There is now a 'mtx' home page at <a href="http://mtx.sourceforge.net">http://mtx.sourceforge.net</a>.
<li> There is now a FAQ that is part of the source code. Please read the
FAQ first. 
<li>Report problems to Eric Lee Green (<a
href="mailto:eric@badtux.org">eric@badtux.org</a>). READ THE FAQ FIRST!
</ul>

<h2> See Also: </h2>
<ul>
<li>The man page for 'mtx'! (once you get it installed). 
<li>T-10 SCSI Working Group home page at <a href="http://www.t10.org">www.t10.org</a>.
<li>The Linux 'sg' SCSI generic driver home page at <a href="http://www.torque.net/sg/">http://www.torque.net/sg/</a>.
<li> <a href="http://badtux.org/eric">The Home Page Of &lt;UL&gt; Tags Anonymous</a> Hi, my name is Eric, and I am addicted to the &lt;UL&gt; tag...
</ul>
    <hr>
    <address>Maintained by <a href="mailto:eric@badtux.org">Eric Lee Green</a><br>
 Hosted by <a href="http://www.valinux.com">VA Linux</a>'s <a href="http://www.sourceforge.net">SourceForge</a></address><br>


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Last modified: Mon Jun 25 15:37:22 MST 2001
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